A wide variety of industries generate volatile and/or other air-borne generally non-particulate materials (for example odors, toxic organics, etc.) as byproducts. These include, for example, businesses such as: wood laminating; composting facilities; rendering plants; breweries; plastics molding; and, fiberglass manufacturing. In general, off-gases from processes conducted in such industries include substantial amounts of undesirable, and sometimes toxic, air-borne materials therein. Also, volatiles or other air-borne contaminants (such as odors) may be released from waste materials of these processes. It is generally undesirable that the process gases or volatiles from said activities be vented directly to the atmosphere. Indeed, environmental legislation, such as the 1990 Clean Air Act Amendment, limits the extent to which certain air-borne materials from such industries can be released.
A variety of techniques are available for removal of such materials from airstreams. One well-known method is incineration. Although incineration is effective, it is not, in many instances, a practical approach. First, there are generally high capital costs and operating costs associated with incineration. Secondly, there are generally air permit problems associated with implementation of new incinerators at various locations.
Activated carbon filters are sometimes used for removal of organics. Often generally involves passage of the air through a carbon filter. A problem is that in time the process generates contaminated carbon, which needs to be disposed of appropriately. Thus, while the technique has some positive effect for removing organics from air, it does not avoid the problem of disposal of contaminated materials. Also, activated carbon systems are not especially effective at removing certain organics which are relatively soluble in water.
Other types of systems which have found some beneficial use include biomass purification systems. In general, in such arrangements the contaminated airstream is passed through a bioreactor or biofilter including an active biomass. Bacteria within the biomass operate on the contaminating materials, often generating acceptable carbon dioxide off-gasses while consuming the organics. When the process is completed, the biomass, comprising the bacteria, typically does not contain substantial amounts of contaminants, and thus can be readily discarded, in safe manners.
While biomass arrangements provide significant advantage, to date they have not been as flexible and efficient as desired. What has been needed has been improvements in biomass air filtration arrangements, to enhance operation.